U.S. Pat. No. 4,993,161 (hereinafter called "prior art") disclosed a laser beam level instrument including a laser diode mounted on a pendulous platform suspended from a frame by gold plated Mylar strips which also serve as conductors for supplying power to the diode. The strips are mounted with a 180 degree twist to overcome resistance to Flexing/bending so that the platform moves freely under the influence of gravity to provide automatic self-leveling.
However, the prior art has the following drawbacks:
1. Only A.C. (alternative current) is available for powering the laser diode. If D.C. is applied across each strip (26) the magnetic field around the strips will be affected by the geomagnetic field of the earth and the platform (24) will not pendulate properly. So, the power supply is quite limited.
2. The strips (26) are approximately 0.001 inch, which is too thin and weak, easily broken and damaged.
3. The D.C. power source (34) should be stepped up to be 20 VAC, which is then stepped down to be 2-3 VDC for driving the diode (22), thereby wasting electric energy during the conversion from D.C. to A.C. and from A.C. to D.C., and shortening the service life of the power source of batteries.
4. Several heavy elements such as the step-up and step-down transformers and inverters, the damping magnets (32), and so on, will increase the total weight of the level instrument, causing leveling and handling inconvenience.
The present inventor has found the drawbacks of the prior art and invented the present automatic optical levelling, plumbing and verticality-determining apparatus.